关键词： 预变形   退火   镁合金   微观结构   力学性能  

摘要： 变形镁合金受限于成形工艺,致使其室温成形性较差并且具有较强的各向异性。通过在不同变形条件进行预变形结合退火处理能够有效弱化镁合金织构从而改善镁合金的力学性能。总结并评述了3种预变形方式结合退火处理对镁合金微观组织与力学性能的影响,并对未来的发展提出了建议。

关键词： Duplex coating   Mg alloy   Friction stir welding   Corrosion behavior  

摘要： In this study, the corrosion behavior of duplex coating on friction stir welded AZ31 alloy was investigated by a series of characterization methods and electrochemical tests. The duplex coating consisted of a micro-arc oxidation (MAO) intermediate layer and an electroless nickel (EN) top layer was applied to the friction stir welding (FSW) joint to enhance its corrosion resistance. The experimental results exhibited that the heterogeneous microstructure in the different zones of the FSW joint caused inhomogeneous susceptibilities to local corrosion. The coarse second phase in the heat-affected zone (HAZ) decreased the corrosion resistance. Although the microstructure differed in the different zones, the morphology of the duplex coating is no significant difference in different zones of the FSW joint. The dense EN top layer and porous MAO intermediate layer were bonded by mechanical interlocking because parts of the EN layer were embedded in the micro-pores of the MAO layer. After depositing the duplex coating, the corrosion potential was raised, and the corrosion current density was reduced. Therefore, the duplex coating provided the FSW joint with improved corrosion resistance. The protection mechanism of the duplex coating against corrosion is depicted in schematic diagrams that explain the corrosion behavior and corrosion mechanism.

关键词： 高强镁合金   汽车   力学性能   耐腐蚀性能  

摘要： 测试和分析了汽车用Mg-6Al-3Sn-1Mn高强镁合金的性能。结果表明:镁合金的强度随挤压温度和挤压比的增加先增大后减小,而伸长率反之,腐蚀电位随挤压温度和挤压比的增加先正移后负移。380℃挤压温度下的抗拉强度和屈服强度比320℃挤压温度的分别增大了11.26%、15.89%,腐蚀电位正移了51 mV。与挤压比14相比,挤压比22下的抗拉强度和屈服强度分别增大了10.16%、14.81%,腐蚀电位正移了46 mV,耐腐蚀性能先提升后下降。汽车用Mg-6Al-3Sn-1Mn高强镁合金的挤压工艺参数优选为:挤压温度380℃、挤压比22。

关键词： 镁合金   耐腐蚀   保护涂层   发展现状  

摘要： 在不同的轻量化材料中,镁合金的使用由于一系列极具吸引力的特性而得到迅速发展,已成为一种重要的轻量化材料,但是其低耐磨性和耐腐蚀性则严重阻碍了镁合金的广泛应用。该文对镁合金保护涂层技术中的喷涂、化学转化膜、阳极氧化、电化学镀等技术进行了总结,评述了它们目前的取得的进展和应用现状,以及主要存在的问题和发展方向,并重点对相对先进的气相沉积技术进行了详细介绍。这些总结评述可为镁合金保护涂层技术的开发应用提供一定指导。

关键词： 镁合金   挤压   长程堆垛有序(LPSO)结构   HAADF-STEM   力学性能  

摘要： 采用扫描电子显微镜、电子背散射衍射、透射电子显微镜、高角度环形暗场−扫描透射,分析了Mg-7Gd-5Y-1Nd-xZn-0.5Zr(x=0,1,2,质量分数,%)挤压态合金微观组织结构和力学性能,旨在探索Zn对于合金性能影响的微观机制。结果表明:在Mg-7Gd-5Y-1Nd-0.5Zr合金中添加Zn元素,不仅形成LPSO结构,也促进了Mg5(RE,Zn)颗粒的析出,并与Zr形成Zn-Zr相。LPSO结构不仅能阻碍晶粒长大,细化晶粒;也能够阻碍动态再结晶,从而形成动态再结晶晶粒和变形晶粒共存的双模结构,动态再结晶晶粒为á0001ñ//ED织构,变形晶粒为á1010ñ//ED织构。微米级大尺寸Mg5(RE,Zn)颗粒会导致应力集中,引起裂纹的萌生,降低合金的塑性;均匀分布的亚微米级Mg5(RE,Zn)颗粒起第二相强化作用,并能钉扎晶界,阻碍晶粒长大。对比3种挤压态合金,Mg-7Gd-5Y-1Nd-2Zn-0.5Zr合金获得了最优的力学性能,其抗拉强度、屈服强度和伸长率分别为365 MPa、276 MPa和17.5%。

关键词： Magnesium alloy   Corrosion fatigue   Extension twins   Secondary crack  

摘要： Bio-magnesium alloys have received great attention due to their degradability and *** fatigue failure is a huge challenge in vivo for bio-magnesium alloy *** the eff ects of twinning textures on the corrosion fatigue of magnesium alloys is meaningful for the *** the current study,pre-compression strains of 2%and 4%were carried out on extruded *** effects of twinning texture on the corrosion performance and corrosion fatigue resistance were *** hydrogen evolution tests indicated that twinning texture enhanced the corrosion resistance of longitudinal cross section by improving uniformity of surface *** results of corrosion fatigue tests indicated that the differences in mechanical damage caused by twinning texture dominated the corrosion fatigue behavior under high stress *** secondary cracks of surface deteriorated the corrosion fatigue resistance of the original specimens under low stress *** compact corrosion film and the re-passivation of matrix suppressed the hydrogen induced cracking,thereby improving the corrosion fatigue resistance of the pre-compression specimens.

关键词： 耐腐蚀性   镁合金   疏水   ZIF-L薄膜  

摘要： 为提高镁合金的耐腐蚀性,以镁合金为基体,对其进行预处理后采用原位生长法,在其表面制备了一层ZIF-L薄膜。通过XRD、SEM、接触角测量仪与电化学工作站等设备对不同时间下所制备的样品进行分析。结果表明:4 h制备的样品薄膜,由致密完整的树叶状纳米片组成。ZIF-L薄膜沉积以后,镁合金表面由亲水变成疏水,随着沉积时间的增加,样品的接触角先增大后减小,4 h制备的样品接触角最大达到135.25°,接近超疏水。4 h制备的样品腐蚀电位最高为-1.34 V、腐蚀电流密度最低(0.0143 A·cm-2),低于镁合金基体(腐蚀电位-1.56 V,腐蚀电流密度为0.0624 A·cm-2),这说明通过ZIF-L薄膜的修饰可改善镁合金的耐腐蚀性。

关键词： 镁合金   消失模铸造   真空低压   振动凝固   壳型铸造   双金属铸件  

摘要： 消失模铸造属于颇有特点的精密绿色铸造技术。但镁合金消失模铸造中存在充型能力差、孔洞缺陷严重、凝固组织粗大及力学性能偏低等问题。针对以上问题,国内外开发了几种镁合金消失模铸造新技术,本文主要介绍这些新技术的最新研究进展。真空低压消失模铸造技术,可保证金属液充型平稳,提高镁液充型和补缩能力,保护其充型过程,适于镁合金铸造成形。振动凝固消失模铸造技术,可提高镁合金充型能力、细化组织、明显提高铸件力学性能。消失模壳型铸造技术,可消除或减少消失模铸造易于出现的孔洞、夹杂等缺陷,能生产高质量复杂镁合金精密铸件。镁/铝双金属消失模铸造技术,可低成本直接成形复杂镁/铝双金属铸件。以上新技术都有其自身特点和应用前景。

关键词： Magnesium alloy   Twinning   FEM   Crystal plasticity  

摘要： The present paper performs a two-dimensional numerical study of the interactions between {10 (1) over bar2} ten sile twin and precipitates aligned along basal planes in magnesium alloys. The model consists of an elliptical twin placed in between two rectangular precipitates. Material behavior is modeled using anisotropic elasticity and crystal plasticity. The model represents the situation at the onset of twinning when twins are small and fit in between the precipitates. The results show that precipitates influence the shear stress necessary to accommodate twin by changing the slip critical resolved shear stress (CRSS) values and by acting as obstacles. Thin twins (aspect ratio <0.05) are influenced by both effects while thick twins (aspect ratio >0.1) are influenced by slip CRSS changes. The precipitate thickness plays a crucial role in twin thickening and propagation. Increasing precipitate thickness increases shear stress necessary to accommodate twin and also decreases stress beyond the precipitate which hinders sequential twin propagation. (c) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： AZ61镁合金   轧制温度   晶粒尺寸   孪晶  

摘要： 采用金相显微镜(OM)、扫描电镜(SEM)、万能试验机等研究了320~410℃不同轧制温度对AZ61镁合金显微组织与力学性能的影响。结果表明:AZ61镁合金经不同温度轧制后,晶粒内部均有大量孪晶出现。随着轧制温度的升高,AZ61镁合金晶粒先增大后减小,320℃轧制的合金晶粒尺寸最小,并有大量第二相在晶界处析出。与挤压态试样相比,经过不同温度轧制后,试样的抗拉强度均提高,伸长率均降低。320℃轧制的合金试样的抗拉强度达到385 MPa,伸长率为15.2%,综合力学性能最佳。